1. Field of the Invention
This invention relates to a plasma display panel, and more particularly to a plasma display panel that is adaptive for improving brightness as well as reducing power consumption.
2. Description of the Related Art
Recently, a plasma display panel (PDP) feasible to a manufacturing of a large-dimension panel has been highlighted as a flat panel display device. The PDP usually controls a discharge period of each pixel in accordance with a digital video data to thereby display a picture. The PDP typically includes a three-electrode, alternating current (AC) type PDP that has three electrodes and is driven with an AC voltage as shown in. FIG. 1.
FIG. 1 is a perspective view showing a structure of each cell arranged in a matrix type en a conventional AC type PDP, and FIG. 2 is a plan view showing the sustain electrode pair shown in FIG. 1.
Referring to FIG. 1 and FIG. 2, the conventional PDP includes an upper plate provided with a sustain electrode pair 14 and 16, an upper dielectric layer 18 and a protective film 20 that are sequentially formed on an upper substrate 10, and a lower plate provided with an address electrode 22, a lower dielectric layer 24, barrier ribs 26 and a phosphorous material layer 28 that are sequentially formed on a lower substrate 12. The upper substrate 10 and the lower substrate 12 are spaced in parallel by the barrier ribs 26.
Each of the sustain electrode pair 14 and 16 is comprised of stripe-shaped transparent electrode 14A and 16A having a relatively large width and made from a transparent electrode material (e.g., ITO) to transmit a visible light, and metal electrodes 14B and 16B having a relatively small width to compensate for a resistance component of the transparent electrodes 14A and 16A. In this case, the transparent electrodes 14A and 16A of the sustain electrode pairs 14 and 16 are opposed to each other with having a gap of approximately 60 μm to 80 μm therebetween. The scan electrode 14 is mainly supplied with a scanning signal for a panel scanning and a sustaining signal for a discharge sustaining, whereas the sustain electrode 16 is mainly supplied with a sustaining signal. Electric charges are accumulated in the upper and lower dielectric layers 18 and 24. The protective film 20 prevents a damage of the upper dielectric layer 18 caused by the sputtering to thereby prolong a life of the PDP as well as to improve the emission efficiency of secondary electrons. This protective film 20 is usually made from magnesium oxide (MgO). The address electrode 22 crosses the sustain electrode pair 14 and 16. This address electrode 22 is supplied with an address signal for selecting cells to be displayed. The carrier ribs 26 are formed in parallel to the address electrode 22 to thereby prevent an ultraviolet ray generated the discharge from being leaked into adjacent cells. The phosphorous material layer 28 is coated on the surfaces of the lower dielectric layer 24 and the barrier ribs 26 to generate any one of red, green and blue visible lights. A discharge space is filled with an inactive gas for a gas discharge.
The cell of the PDP having the structure as mentioned above is selected by an opposite discharge between the address electrode 22 and the scan electrode 14, and thereafter sustains the discharge by a surface discharge between the sustain electrode pair 14 and 16. In the PDP cell, the phosphorous material 28 is radiated by an ultraviolet ray generated upon sustain discharge to thereby emit a visible light into the exterior of the cell. In this case, the PDP controls a discharge sustain period, that is, a sustain discharge frequency of the cell in accordance with a video data to thereby implement a gray scale required for an image display.
Such an AC surface-discharge PDP is driven with being divided into a plurality of sub-fields, so as to realize gray levels of a picture. A light-emission having a frequency proportional to a weighting value of a video data is made in each sub-field period to thereby express a gray level. For instance, if it is intended to display a picture of 256 gray levels using an 8-bit video data one frame display interval (i.e., 1/60 second=about 16.7 msec) at each discharge cell 11 is divided into 8 sub-fields SF1 to SF8. Each of the 8 sub-fields SF1 to SF8 again is divided into a reset period, an address period and a sustain period, and the sustain period is given bad a weighting value at a ratio of 1:2:4:8, . . . , :128. Herein, the reset period is a period for initializing the discharge cell; the address period is a period for generating a selective address discharge in accordance with a logical value of a video data; and the sustain period is a period for sustaining a discharge at the discharge cell having generated the address discharge. The reset period and the address period are identically assigned in each sub-field interval.
If electrode widths of the scan electrode 14 and the sustain electrode 16 are defined narrowly in order to reduce power consumption of such a PDP, then a discharge path upon discharge is shortened to thereby limit a light-emission area. Thus, an emission amount of an ultraviolet ray is reduced and hence brightness is deteriorated. On the other hand, if electrode widths of the scan electrode 14 and the sustain electrode 16 are defined widely in order to enhance brightness of the PDP, then a capacitance value rises to increase a discharge current and power consumption.
Furthermore, the conventional PDP is made into a larger dimension screen than other flat panel display (FPD) devices having 40, 50 and 60 inches, etc. Accordingly, in the conventional PDP, a voltage drop caused by an electrode length has a relatively large difference between the middle portion and the peripheral portion of the PDP. Also, since a discharge gas is injected into the interior of the PDP at a lower pressure than the atmospheric pressure, a force applied to the substrates 11 and 16 at the middle portion where the upper/lower substrates 10 and 12 are supported only by the barrier ribs 26 becomes different from that at the peripheral portion where the upper/lower substrates 10 and 12 are joined with each other by a sealant (not shown). As a result, although the conventional PDP has somewhat difference depending upon a size of the panel, it has a brightness difference between the middle portion and the peripheral portion thereof in each of the horizontal direction and the vertical direction to thereby cause a non-display area at which any discharge does not occur.